Joseph Marshall Flint 13 
absence of the Bronchus cardiacus, destroys the absolute symmetry of the 
hyparterial region. His followed the successive appearance of the chief 
bronchi and their main branches by the reconstructive method as far as 
embryos of the second month. 
The growth of the tree occurs according to His by an extension of the 
root branches and a division of the end buds. In no place did he find 
evidences of lateral budding. ‘The end buds during the process of divi- 
sion lose their conical form and flatten to some extent, while an elevation 
appears on one side which through the formation of a furrow leads to the 
outgrowth of two separate enlargements from the original bud. By the 
acquisition of cylindrical status on the part of these secondary buds the 
process can repeat itself. Below the region of the 3d hyparterial bronchus 
a point is reached where one cannot hold strictly to the principle of 
monopodial division, for it is impossible, His believes, to make as Aeby 
does the principles of monopodial and dichotomous division mutually 
exclusive. This, His remarks, is a conception of a somewhat transcen- 
dental nature, which leads the zealous investigator to personify his own 
ideas in the organ. The causes which control the form development of 
a growing tissue need not always remain the same, but may change its 
character once or several times. Accordingly, His summarizes the growth 
process from the unpaired anlage of the lung, which extends to either 
side in paired dilatations. From these primary sacs, lateral sprouts 
appear by monopodial growth. Further division is by dichotomy and 
finally a point is reached where the division occurs by more or less 
abundant lateral budding. 
Willach, 88, studied several stages of the development of the lungs in 
the mole and pig, but his material, however, was not sufficient to give 
him a very complete picture of the gradual evolution of the pulmonary 
apparatus so he used the findings of other investigators to fill the gaps. 
Although Willach’s own specimens did not include the stages of the first 
division of the primitive bronchi he believes the growth from first to 
last is monopodial, the end bud developing a lateral bud before its lumen 
narrows. ‘These lateral buds become cylindrical as the parent bronchus 
continues to grow. Willach concludes from a study of the illustrations 
in His’ paper that the eparterial bronchus is a derivation of the first 
ventral bronchus and looks upon it as an accessory branch in the sense of 
Aeby. He likewise believes that the apical branch of the Ist left ventral 
bronchus is analogous to the eparterial branch because, on its side, it 
bears the same relationship to the first lateral branch of the pulmonary 
artery that the eparterial does on the left. Willach follows the ideas 
of His in believing the Bronchus cardiacus is an independent lateral 
